simply put... if candidate 8 and 9 do not exist in r6c8 then the UR is forced to exist...
therefore, any other candidates in r6c8 cannot exist, this eliminates the 2,3 and 4 from r6c8 and solves the puzzle.
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this alternative way of viewing the UR is, for my money, easier than noticing that the {1,3,4} naked triple in column 8 exists because of the UR.